Space.com

What's Hot This Week Monster Black Holes Are Most Massive Ever Discovered by Charles Q. Choi, SPACE.com Contributor Two newly discovered black holes tip the scales at more than 9 billion times the mass of our sun. NASA Fires Up Engine for Giant New Rocket SPACE.com Staff The J-2X engine will power the second stage of NASA's new heavy-lifter. Sponsored by: Milky Way's Galactic Gobbling Leaves Star 'Crumbs' Vote Now! Top Space Stories of the Week - Dec.4, 2011